I have a Compaq nx8220 that I've had for a few years and lately, when I turn it on in the morning, there's a sort of rasping sound, as the operating sytem loads - maybe the internal fan? 

I could be wrong, but it seems to be related to the cold mornings we've been having lately.

I'm wondering if it would be better not to turn it off at night?  I know that it's recommended you don't turn off desktops, but what about laptops?

If your advice is not to turn it off, what sort of power settings should I have?  Should I let it go into hibernation, for instance?

Any advice would be much appreciated.  :)